It is well known to use an inflatable cuff to occlude blood flow into a human limb and to maintain such occlusion for an extended period to provide a bloodless surgical field in the portion of the limb distal to the cuff. It is also well known to employ an inflatable cuff to indirectly measure the blood pressure of a human by controlling blood flow into the patient's limb.
Human limbs may have an uneven or tapered configuration at any particular location along the limb. Most of the inflatable cuffs in the prior art do not conform well to the tapered non-cylindrical areas of limbs often subjected to occluding devices, resulting in the use of cuff pressures higher than actually required to obtain an occlusive effect for surgery due to the reduced effective area of contact between the cuff and the limb. The use of an unnecessarily high pressure and a cuff with a narrow effective area of contact is hazardous to the patient. Cuffs in the prior art which are intended to conform to a non-cylindrical shape, such as a tapered limb, do not tend to be adjustable over a range of tapered shapes and therefore the exact shape must be known or measured before selection and application of a cuff which will conform well to the tapered shape. This procedure is not practical and would require an unrealistically large inventory of cuffs. A mismatch of cuff shape and limb shape results in the patient being subjected to various hazards. One such hazard is a reduced effective area of contact between the cuff and limb which necessitates the use of higher and less safe inflation pressures to maintain a bloodless surgical field. Another hazard is an increased tendency of the cuff to creep down the patient's limb to a point where the surgical field may be obstructed or where the bladder may be fully distended without producing an occlusive effect. In some prior art cuffs there is an increased tendency for concentric layers to separate axially and `telescope` down the patient's limb thereby losing the occlusive effect. Thus a larger volume must be filled with pressurized gas to initially occlude blood flow into the limb or to rapidly change the applied pressure in order to remain near the minimum safe pressure.
Prior art cuffs generally have only one means or dependent means for securing the cuff around the limb and the cuffs are rendered ineffective by a malfunction of the securing means. Many cuffs have materials and constructions which make the cleaning and reuse of the cuff difficult and time-consuming. Many are too expensive to make it feasible to consider disposal after a single use. Many of the prior art cuffs do not have inflatable bladders which completely encircle the limb. This is undesirable in surgical applications because greater displacements of the tissues beneath such cuffs may result and lead to injuries. Prior art cuffs have not been formed on or adjusted to a curved surface during fabrication and this may increase the likelihood that soft tissue beneath the cuff may be pinched or injured as the cuff is inflated, or that a separate bandage of soft material must be required beneath the cuff to reduce this pinching tendency. A bandage of this type may impair the effectiveness of the cuff and increases the complexity, time and cost of cuff application. No cuff known in the prior art contains means for determining the adequacy of the application to the limb so that the method of application may be adjusted or standardized in order for the cuff to be applied too loosely or too tightly, either of which may be hazardous.
The applicant is aware of the following U.S. patents which are more or less relevant to the subject matter of the applicant's invention.
______________________________________ 3,756,239 9/1984 Smythe 128/327, 128/2.05C 2,347,197 4/1944 LaLiberte 128/327 3,120,846 2/1964 Fletcher 128/327 3,570,495 3/1971 Wright 128/327 3,504,675 4/1970 Bishop 128/327 3,670,735 6/1972 Hazlewood 128/327 3,587,584 6/1971 Keller 128/327 3,977,393 8/1976 Kovacic 128/327 4,106,499 8/1978 Ueda 128/327 3,699,945 10/1972 Hanafin 128/2.05 C, 128/327 3,467,077 9/1969 Cohen 128/2.05 2,811,970 11/1957 Hipps 128/327 ______________________________________
The following U.S. patent applications of the applicant are more or less relevant to the subject matter of the applicant's invention.
U.S. application Ser. No. 337,152; Title: Adaptive Pneumatic Tourniquet; Art Unit: 336; Inventor: McEwen.
U.S. application Ser. No. 451,610 Title: Pneumatic Tourniquet; Art Unit: 336; Inventor: McEwen.
U.S. application Ser. No. 375,557; Title: Occlusive Cuff; Art Unit: 335; Inventor: McEwen.
The applicant is also aware of the following published references which are more or less relevant to the subject matter of the applicant's invention.
J. A. McEwen and R. W. McGraw, "An adaptive tourniquet for improved safety in surgery,"IEEE Transactions in Bio-Medical Engineering, Vol. BME-29, February 1982, pp. 122-128.
L. A. Geddes and S. J. Whistler, "The error in indirect blood pressure measurement with the incorrect size of cuff," American Heart Journal, Vol. 96, 1978, pp. 4-8.